The present invention relates to a radiosensitive composition which can be utilized in coating materials, printing materials, UV ink, photoresists for semiconductors, photoresists for printed circuit board, materials for holography, etc.; and an aryl triflate compound, an photo-acid-producing (or generating) agent (or photo acid generator) or an photo-acid-producing agent system, which is suitable for said radiosensitive composition.
Practical use of photochemical cationic polymerization was made possible by use of a thermally stable onium salt found by J. V. Crivello (J. V. Crivello and J. H. Lam, Macromolecules, vol. 10, p. 1307 (1977), etc.). In the photochemical cationic polymerization, as compared with conventionally used photochemical radical polymerization, the polymerization is not inhibited by air and the lifetime of an active species is longer. Therefore, the photochemical cationic polymerization is advantageous, for example, in that living polymerization is possible and monomers can be selected in a wide range. Accordingly, earnest studies are in progress in this field. Recent results of investigation on the photochemical cationic polymerization are reviewed in detail in UV Curing: Science and Technology, vol. 1 (1978) and vol. 2 (1984), Technology Marketing Corporation, Norwalk, Conn. A so-called chemical amplified photoresist has been proposed by a group belonging to International Business Machines Corp. The chemical amplified photoresist is highly pervious to excimer laser and has high sensitivity and resolution. Therefore, it is noted as a photoresist for microfabrication of a semiconductor (M. J. Bowden and S. R. Turner, "Polymers for High Technology Electronics and Photonics," ACS Symposium Series, U.S. Chemical Society, Washington, D.C. (1987) p. 138, etc.).
Both photochemical cationic polymerization system and chemical amplification system comprise as their essential constituent a compound or a system, which produces a strong acid on light irradiation. In the case of heretofore known onium salts such as triaryl sulfonium salts and diaryl iodonium salts, the quantum yield of acid production is relatively high and the strength of an acid produced is sufficient, but the onium salts are disadvantageous, for example, in that a light source is limited because wavelengths at which they are photosensitive are short, that they have a bad compatibility with generally used resin systems, that they contain metals, resulting in doping unnecessary in the semiconductor field, and that soft errors due to radioscopes take place. Efforts have been made in various fields to overcome these disadvantages. For example, S. P. Pappas, i.e., one of the present investigators, and his co-workers found that the onium salts are photochemically sensitized by anthracene and the like, whereby application of the onium salts in the near ultarviolet range was made possible (S. P. Pappas, Journal of Polymer Science, Polymer Chemistry Edition, vol. 22, p. 77-84 (1984). There was attempted a method in which the onium salts were improved in compatibility with resin systems by introducing an alkyl group into the aryl group. In the process disclosed in Japanese Patent Unexamined Publication No. 63-272977, application of the onium salts in the semiconductor field is made possible by converting them into onium salts which contain a counter ion but not a metal.
Acid-producing agents other than the onium salts have also been investigated. For example, there have been disclosed cases in which there are used o-nitrobenzyl tosylate (L. F. Thompson, E. Reichmanis, F. M. Houlikan and R. G. Tarascon, Proceedings of the ACS Division Polymeric Materials: Science and Engineering, vol. 60, p. 137 (1989)), trichloromethyl-s-triazine (Japanese Patent Unexamined Publication Nos. 61-169835 and 61-169837), and a sulfonyl compound (Japanese Patent Unexamined Publication No. 61-166544). However, when these acid-producing agents are used, the strength of acids produced is not sufficient. There are also known mixed ligand arene cyclopentadienyl Fe (II) salts (J. Lohse and H. Zweifel, Advances in Polymer Science, vol. 78, p. 61 (1986)), but they are not free from the defects described above, namely, they contain a metal and are ionic. Thus, there is not known a radiologically-acid-producing agent which can be subjected to spectral sensitization for impartment of sensitivity to a generally used radiation source, contains neither ionic bond nor metal atom, has a sufficiently high efficiency of acid production by radiation irradiation, gives an acid having a high strength, and has a high storage stability.